A research team led by Prof. CHEN Xianhui from the University of Science and Technology of China (USTC), collaborating with the team led by Prof. SUN Jian from Nanjing University, realized new high superconducting transition temperature of 36 K in elemental materials under high pressure. The study was published in Physical Review Letters.
Elemental materials provide clean and fundamental platforms for studying superconductivity. Since the discovery of superconductivity in the element mercury by the Dutch scientist Onis in 1911, more than 50 elements in total have been found to show superconductivity under atmospheric environments or high pressures. However, most elements have low superconducting critical temperatures (Tc), with the highest previous elemental Tc of 26 K being achieved by elemental titanium (Ti) at high pressures.
Previous studies revealed that elemental scandium (Sc) undergoes four structural phase transitions under pressure. While due to the limitations of early high-pressure experimental techniques, mysteries on the superconductivity of elemental Sc at higher pressures remain to be revealed.
To address this issue, researchers studied the transport of elemental Sc at ultra-high pressures and determined its superconducting phase diagram at high pressures. Tc was found to increase rapidly with increasing pressure in the Sc-II phase by high voltage electrical transport measurements, which is consistent with earlier reports.
Besides, researchers explored the physical origin of the large increase in superconducting Tc at high pressure through first-principles calculations and found that the strong coupling between d electrons and moderate-frequency phonons in the Sc-V phase is the most important factor for its high Tc.
The findings of this study showed that the Tc of elemental Sc under pressure is closely related to its structure. The 36 K Tc found in the Sc-V phase not only sets a new record for elemental Tc, but also sheds light on finding high-temperature superconducting materials in simple systems.、
Phase diagram of the evolution of Tc of elemental scandium with pressure (Image by Prof. CHEN et al.)
(Written by HUANG Rui, edited by SHU Yukang, USTC News Center)